The objective in permanent or irreversible bonding of substrates is to produce an interconnection which is as strong and especially as irreversible as possible, therefore a high bond force, between the two contact surfaces of the substrates. There are various approaches and production methods for this in the prior art.
The known production methods and the approaches which have been followed to date often lead to results which cannot be reproduced or can be poorly reproduced and which can hardly be applied especially to altered conditions. In particular production methods which used at present often use high temperatures, especially >400° C. in order to ensure reproducible results.
Technical problems such as high energy consumption and possible destruction of structures which are present on the substrates result from the high temperatures of partially far above 300° C. which have been necessary to date for a high bond force.
Other demands consist in the following:
front-end-of-line compatibility.                This is defined as the compatibility of the process during the production of the electrically active components. The bonding process must therefore be designed such that active components such as transistors, which are already present on the structure wafers, are neither adversely affected nor damaged during the processing. Compatibility criteria include mainly the purity of the chemical elements (mainly in CMOS structures) and mechanical loadability, mainly by thermal stresses.        
low contamination.
no application of force.
The reduction of the bond force leads to more careful treatment of the structure wafer and thus to a reduction of the failure probability by direct mechanical loading.